Method for separating hydrocarbon vapors



Jan. 19, 1932. F. A. HOWARD ET AL METHOD FOR SEPARATING HYDROCARBON VAPORS Filed Nov. 18. 1927 NKNUESNUESN N NRNSO \SQRRNOQNT 5 vwemro 2 Frank (2'. Howard 22am anze! 6. z 0 0mm. 5 51 M 1 H0114 e Patented Jan. 19, 1932 UNITED STATES PATENT OFFICE FRANK A. HOWABIL OE ELIZABETH, AND NATHANIEL E. LOOHIS, 0] 'WESTII'IELD, NEW JERSEY, ASBIGNOBS T0 STANDARD OIL DEVELOPMENT COMPANY, A CORPORATION 01' DELAWARE Application filed November is, 1927. Serial No. 234,077.

petroleum oil is flowed through a zone in which it is heated under pressure to a cracking temperature and thereafter held in a digesting zone in which further crackmg takes place. Cracked material is withdrawn in a continuous stream from the digesting zone and is ordinarily fractionated to separate therefrom a liquid containing principally the hydrocarbons'of higher boiling point than the gasoline fraction, leaving a vapor phase containing substantially all the gasoline hydrocarbons produced by cracking. Our mvent-ion has for its objects the more efliclent recovery of gasoline from said vapor phase and the production of a gasoline of enhanced stability.

The drawing shows a diagrammatic vertical cross section of apparatus adapted to carry out the preferre embodiment of our method. The drawing and method of operation will be conjointly described. The hydro carbon vapors, from which hydrocarbons of higher boiling point than it is desired to mclude in gasoline have beenremoved, are supplied to the apparatus from a number of cracking installations through pipes 1, 2, 3

and 4, discharging into pipes 5 and 6 and passing into rectifying towers 7 and 8, WhlCh are connected in parallel. These towers are preferably of the plate type and any number may be employed in parallel, depending on the capacity required. The plates 9 and 10 carry overflow pipes and vapor distributors, such as bellcaps, which, however, are not shown. Partial condensers 11, 12, 13 and 14 are located in the upper part of these towers by means of which the vapors may be partially condensed by the circulation of a cooling medium such as water and/or cold feed stock passing to the cracking apparatus.

METHOD FOR SEPABATI [NG HYDROOABBOII' VAPOR/B Heater coils 15 and 16 are located in the base of towers 7 and 8 respectively.

These towers are preferably operated under a pressure in excess of atmospheric, lbs. gauge having been found very suitable. The amount of cooling medium supplied to the condensers 11, 12, 13 and 14, is preferably so adjusted that the product taken overhead will have an end point ranging from 300 to 360 F. The term .end point as herein applied to a vapor phase denotes that if a sample of said vapor phase were completely condensed and redistllled at normal pressure it would show a maximum vapor temperature corresponding to end point mentioned. This passes off through pipes 17 and 18 discharglng 1nto pipe 19.

The amount of heating medium e. g. steam supplied to the heater 00118 15 and 16 is referably so adjusted that the liquid with raw from the oase of columns 7 and 8 through pipes 20 and 21 discharging into pipe 22, is su stantially free from constituents boilin below 360 F. This material is conducted through the cooler 23 discharging into pipe 24. It may pass directly through pipe 24 controlled by valves 25, 26 and 27 to the pump 28, but is preferably diverted through pipe 29 controlled by valve 30 to any suitable treating apparatus, diagrammatically indi cated by the numeral 31, in which it is treated with sulfuric acid followed by an alkali and water wash, and with doctor solution if needed to the extent necessary to cause it to conform to market specifications and continuously returned to the system through pipe 32 controlled by valve 33.

The vapors passing overhead throu h pipe 19 are discharged into the interm ate or lower part of fractionating column 34. This is equipped with plates 35 which carry overflow pipes and vapor distributors (e. g. bellcaps), not shown. Column 34 is preferably operated under substantially the same pressure as columns 7 and 8. The vapor passing overhead through ipe 36 discharges into partial condenser 3 which may be cooled in any suitable manner.- The l1qu1d products condensed in 37 pass through pipe 38 into the receiving drum 39. Uncondensed gases are diverted throu h pipe 40 while liquid condensate is wit drawn throu h pipe 41 to pum 42 and elevated intot e upper part of column 34 through pipe 43. The amount of cooling in 37 is so regulated that thevapors passin ofi through'40 conslst prmipmlly of hy rocarhons normally gaseous. eater coil 44 is located in the bottom of column 34 and the amount of heat supplied thereby is so proportioned that liquid withdrawn from the base of column 34 by means of pipe 45 is substantially free of normally aseous constitutents. This liquid is assed t rough cooler 46' and is thereafter charged into finished gasoline pipe 47.

The hydrocarbon vapors passing through pipe 40 are introduced in the lower part of absorption tower 48. This-tower is equipped with a series of plates 49, which carry overflow pipes and vapor distributors (e. g. bellcaps), not shown. This tower is preferably operated under substantially the same pressure as columns 7, 8 and 34.

An absorption menstruum is supplied to the column by means of pipe 50 and spray distributor 51. This menstruum preferably consists of part of the oil which has been treated and reintroduced into the system through pipe 32. The amount of absorption menstruum is preferably so proportioned that only propane and hydrocarbons of lower boiling point escape through pipe 52, passing thereby into any suitable accumulator. The liquid withdrawn from the base of 48 by means of pipe 53 is passed by means of pump 54 discharging through pipe 55, coil 56 and pipe 57 into the intermediate or lower part of a stabilizing column 58. This column is equipped with plates 59 which carry overflow pipes and vapor distributors (e. g. bellcaps) not shown, and is preferably operated under a reduced pressure, 5 lbs. gauge having been found particularly suitable. This column maybe supplied with absorption menstruum through pipe 60, discharging into spray distributor 61 and may be heated at the base by steam introduced through pipe 62 to coil 63, the steam condensed passing off through pipe 64. The absorption menstruum introduced through pipe preferably comprises the treated naphtha which has been re-introduced to the system through pipe 32 in excess of that supplied to distributor 51 through pipe 50. The amount of steam introduced to coil 63 is so proportioned that substantlally only propane and hydrocarbons of lower boiling point are evolved and pass off through pipe 65 into pipe 52. The residuum from the stabilizer column 58 is withdrawn through pipe 66 and introduced by means of pump 67 to the chamber 68 to pass in heat exchanging relationship to the oil flowing to column 58, thereafter passing off through pipe 69, to cooler 70, and then by means of pipe 71 into pipe 47. All of the products passing into cooler 46 and combining therein are of stable character and conform to market specifications and may be diverted to any suitable accumulator.

It will be understood that the equipment shown is in illustration and not in hmitation and that various alternative procedures may be adopted within the scope of the appended claims, in which it is our intention to claim broadly all novelty inherent in our invention.

We claim 1. The method of converting mixed hydrocarbons consisting principally of compounds of the gasoline senes into marketable products which comprises subjecting said hydrocarbons in the form of vapors to fractional condensation under rectifying conditions to produce a first vapor phase and a first liquid residue, treating the first liquid residue to remove undesirable constituents therefrom, further fractionating said first vapor phase to produce a second vapor phase comprising I hydrocarbons normally gaseous and a second liquid residue, passing all of said second vapor phase into countercurrent relationship to an absorption medium consisting of said first liquid residue after treatment separating constituents lower boiling than butane from the charged absorption medium and combining said absorption medium after the separation of lower boiling constituents with the second liquid residue.

2. Method according to claim 1, in which the quantity of absorption medium is suflicient to absorb all constituents of higher boiling point than propane.

3. Method according to claim 1, in which the first light'vapor phase has an end point of from 300 to 360 F.

4. Method according to claim 1, in which the further fractionation of vapors is carried out at a pressure of approximately 50 lbs. per square inch. I

5. Method of converting mixed hydrocarbons consisting principally of compounds of the gasoline series into marketable products, which comprises subjecting said hydrocarbons in the form of vapors to fractional condensation under rectifying conditions to produce a first vapor phase and a first liquid residue, treating the first liquid residue to remove undesirable constituents therefrom, further fractionating said first vapor phase to produce a second vapor phase comprising hydrocarbons normally gaseous and a second liquid residue, passing all ofsaid second vapor phase into countercurrent relationship to an absorption medium consisting of said liquid residue after treatment, maintaining a pressure of about 50 pounds per square inch during the two fractionation and absorption steps, heating and fractionating the absorption medium after absorption to obtain and a liquid substantially free of constituents lower boilin than butane, maintaining a pressure of about 5'lbs. per uare inch above the atmoslpheric pressure durmg the fractionation of t e absorption medium after absorption and combining the absorption medium which has been freed from constituents lower boiling than butane, with said second liquid residue.

FRANK A. HOWARD. NATHANIEL E. LOOMIS. 

